CVE-2026-48747Network attack vector

Unauthenticated webhook forgery via HMAC algorithm downgrade

Published Jul 14, 2026 · Updated Jul 14, 2026

Signature downgrade in Symfony Mailomat Mailer Bridge before 7.4.13 and 8.0.13 allows remote attackers to forge webhook requests. MailomatRequestParser::validateSignature() passes the algorithm named in X-MOM-Webhook-Signature directly to hash_hmac() instead of requiring SHA-256. Exploitation requires a configured, reachable Mailomat webhook and the ability to compute a signature under a weaker PHP-supported HMAC primitive; the request is then accepted as an authentic Mailomat event.

CVSS severity6.3
Medium
EPSS probability0.25%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Signature downgrade in Symfony Mailomat Mailer Bridge before 7.4.13 and 8.0.13 allows remote attackers to forge webhook requests. MailomatRequestParser::validateSignature() passes the algorithm named in X-MOM-Webhook-Signature directly to hash_hmac() instead of requiring SHA-256. Exploitation requires a configured, reachable Mailomat webhook and the ability to compute a signature under a weaker PHP-supported HMAC primitive; the request is then accepted as an authentic Mailomat event.

The record

CVE
CVE-2026-48747
Published
Jul 14, 2026
Updated
Jul 14, 2026
Vendor
Symfony
Product
Symfony
Classifications
CWE-347, CWE-757, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 14, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 14, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 7.2.0, < 7.4.12
  2. Affected versionversion=>= 8.0.0-BETA1, < 8.0.13

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Symfony · Symfonyversion=>= 7.2.0, < 7.4.12; version=>= 8.0.0-BETA1, < 8.0.13
Symfony · Symfony Mailomat Mailer Bridgeversion=>= 7.2.0, < 7.4.12; version=>= 8.0.0-BETA1, < 8.0.13

Published CVSS scores

6.3GitHubCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
5.3NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-347Improper Verification of Cryptographic Signature
CWE-757Selection of Less-Secure Algorithm During Negotiation ('Algorithm Downgrade')
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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